Cryo-EM structure of the endothelin-1-ETB-Gi complex

  1. Fumiya K Sano
  2. Hiroaki Akasaka
  3. Wataru Shihoya
  4. Osamu Nureki

  • Curated by eLife

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    eLife assessment

    Based on the Cryo-EM structure of human ETB in complex with the vasoconstricting peptide ET-1 and the inhibitory G-protein (Gi), this valuable study presents convincing data on how agonist binding is coupled to Gi-protein binding. The complex structure is solid and will appeal to the GPCR and pharmacology communities.

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Abstract

The endothelin ET B receptor is a promiscuous G-protein coupled receptor that is activated by vasoactive peptide endothelins. ET B signaling induces reactive astrocytes in the brain and vasorelaxation in vascular smooth muscle. Consequently, ET B agonists are expected to be drugs for neuroprotection and improved anti-tumor drug delivery. Here, we report the cryo-electron microscopy structure of the endothelin-1-ET B -G i complex at 2.8 Å resolution, with complex assembly stabilized by a newly established method. Comparisons with the inactive ET B receptor structures revealed how endothelin-1 activates the ET B receptor. The NPxxY motif, essential for G-protein activation, is not conserved in ET B , resulting in a unique structural change upon G-protein activation. Compared with other GPCR-G-protein complexes, ET B binds G i in the shallowest position, further expanding the diversity of G-protein binding modes. This structural information will facilitate the elucidation of G-protein activation and the rational design of ET B agonists.

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  1. Version published to 10.7554/elife.85821 on eLife
  2. eLife

    eLife assessment

    Based on the Cryo-EM structure of human ETB in complex with the vasoconstricting peptide ET-1 and the inhibitory G-protein (Gi), this valuable study presents convincing data on how agonist binding is coupled to Gi-protein binding. The complex structure is solid and will appeal to the GPCR and pharmacology communities.

  3. eLife

    Reviewer #1 (Public Review):

    The endothelin ETB receptor is a G-protein coupled receptor activated by vasoactive peptide endothelins, causing vaslorelaxtion in smooth muscle. By determining the Cryo EM structure of human ETB in complex with the vasoconstricting peptide ET-1 and the inhibitory G-protein (Gi), the study represents a convincing insight into agonist-induced receptor activation and transducer-coupling. The complex structure is solid and will appeal to the GPCR and pharmacology communities.

    Strengthens: The authors have managed to obtain the first G-protein complex structure of an ETB receptor by working with a receptor that still retains G-protein coupling (i.e. not a thermostabilized mutant) and by developing new methodologies into how the G-protein is remotely tethered to the GPCR. The Cryo EM structural details highlight clear differences into how the G-protein binds that also includes the more downward movement of TM7.

    Weaknesses: While it is technically challenging to obtain an endothelin-1-ETB-Gi complex, the fusion approach means that there is equilibrium is already pushed towards a complex that may otherwise require lipids, such as PIP2. Whilst I don't know what may alter how alpha 5 interacts with ETB, this cannot be ruled out either.

  4. eLife

    Reviewer #2 (Public Review):

    This study adds value in the relatively new field, specifically in the topic of ET-B receptor. In this study the authors provide a new structure in ET-B receptor that might be beneficial to the development of ET-B agonist. However, from the clinical and physiological point of view, the manuscript did not provide sufficient evidence in its current form.

  5. eLife

    Reviewer #3 (Public Review):

    This manuscript by Sano et al., presents cryo-EM structure of endothelin-1-bound endothelin B receptor (ETbR) in complex with heterotrimeric G-proteins. The structural snapshot provides important information about agonist-induced receptor activation and transducer-coupling. This manuscript also designs and present a successful case example for a variation of previously used NanoBiT-fusion-based strategy to stabilize GPCR-G-protein complexes. This strategy may be broadly applicable to other GPCR-G-protein complexes as well, and therefore, also provides an important methodological advance. Overall, the experimental design and interpretation of the structure are excellent, and the manuscript present an easy-to-follow coherent story. Considering the importance of ETbR signaling in multiple physiological and disease conditions, this structural snapshot, taken together with earlier structural studies by the same laboratory, advances the ETbR biology significantly with potential for novel ligand discovery. This manuscript is also available as a preprint in bioRxiv as well as another manuscript from Xu and Jiang group. Considering the structural information presented in these manuscripts, I would strongly suggest that even if the other manuscript is published somewhere before this one, it should not be viewed as a compromise on novelty, and rather considered as complementary information from independent studies that further strengthen the impact.

  6. Version published to 10.1101/2023.01.12.523720v1 on bioRxiv